The present invention relates to characterization of the iso-dense effect. More particularly, but not exclusively, the present invention relates to determining the iso-dense effect for microdevice manufacture.
To increase the speed of electronic devices, it is often desirable to decrease the critical dimension of various semiconductor components. Concomitantly, functionality of many integrated circuit devices may be increased by reducing the size of individual components so that the component density, and correspondingly the number and complexity of integrated circuits formed from the components may be increased. Unfortunately, as the critical dimension of semiconductor devices is deeply scaled down into the submicron range ( less than 0.5 micron), various shortcomings of the processes used to make such devices can become of greater concern.
For lithographic processes aimed at forming devices with dimensions in the submicron range, the iso-dense effect can become more prominent. The iso-dense effect results in a difference in transfer dimension for dense features as compared to features that are more greatly spaced apart. This phenomenon is commonly encountered as a linewidth transfer difference between an isolated line of submicron width and a denser lines of comparable width with submicron spacing. Wilder and Singh et al., Sub-0.35-Micron Critical Dimension Metrology Using Atomic Force Microscopy, SPIE Proceedings, volume 2725, pages 540-554 (published 1996) provides information concerning existing techniques to evaluate the iso-dense effect and is incorporated by reference in its entirety herein.
Notably, characterizing the iso-dense effect can be complicated by the fact that measurement tools, such as a Scanning Electron Microscope (SEM), can be sensitive to the iso-dense condition. As a result, special tools are sometimes used, such as the Atomic Force Microscope (AFM), and/or electrical measurements are made; however, these approaches can be slow and expensive, and generally cannot be performed in real time with the desired manufacturing process. Other measurement schemes include application of a Transmission Electron Microscope (TEM); however, such schemes are typically destructive and require long sample preparation times. Consequently, further contributions are needed in this area of technology.
One embodiment of the present invention includes a unique technique to characterize the iso-dense effect. Other embodiments of the present invention include unique systems, methods, and apparatus to determine the iso-dense effect for microdevice manufacture.
A further embodiment of the present invention includes the definition of a pattern on a substrate for manufacture of a microdevice. This pattern includes a dense feature region and an isolated feature region. A portion of one or more features in the dense feature region are removed and one or more measurements are made corresponding to at least one of the remaining features after this removal. An iso-dense effect is determined from the measurements.
A further embodiment includes: defining a pattern on a substrate that includes a dense region of features and an isolated feature region comprised of at least a part of one of the features; measuring at least one of these features at a number of different points relative to the isolated and dense regions with a measurement tool; and determining an iso-dense effect for the measurement tool from these measurements.
Still another embodiment of the present invention includes a mask having a central portion to define a layer of one or more integrated circuits, a first end portion to define a first pattern including a dense region of features, and a second end portion opposite the first end portion to define a second pattern including one or more windows. During operation, the mask is arranged to overlap one or more of the features of the first pattern when making one field with one or more windows of the second pattern when making an adjacent field. From these overlapping patterns, a set of measurable marks are provided to determine an iso-dense effect.
Yet another embodiment includes a device having an iso-dense effect evaluation pattern comprised of a number of approximately parallel line segments, with at least one of the line segments being provided as a reference mark measurable at different points to determine one or more iso-dense effects. In one form, the reference mark extends from a dense region of the line segments to an isolated region to provide an isolated portion. This isolated portion is separated from the other line segments by a distance greater than the minimum spacing of the line segments in the dense region.
Accordingly, one object of the present invention is to provide a unique technique to characterize an iso-dense effect.
Another object of the present invention is to provide a unique method, system, or apparatus to determine an iso-dense effect for the manufacture of a microdevice.
Further objects, features, aspects, forms, embodiments, benefits, and advantages of the present invention shall become apparent from the description and figures contained herein.